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I am supposed to determine the direction a windmill is facing from aerial images (with respect to True North - 0 to 359 degrees).

My question is, how can I determine the correct direction of the windmill and calculate its angle relative to the y-axis? Thanks!

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    You already have the box points, can you use the points to get the angle of the box? Commented Sep 12, 2017 at 10:07
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    Yes, but the biggest issue is figuring out if the windmill is pointing (in this case) to the upper-left (correct) or bottom-right (incorrect). Commented Sep 12, 2017 at 10:11
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    calculaing that blobs centroid's position in the bounding box should give you the direction... how long have you been thinking about this? 2 minutes? Commented Sep 12, 2017 at 10:14
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    I'd say gathering data from the windpark is not exatly obvious (and very off-topic given the question) Commented Sep 12, 2017 at 10:49
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    @Piglet that's not very practical and in that case he won't need computer vision to do that which is not what he wants on his project Commented Sep 12, 2017 at 10:50

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Do not know if this works in general, but given your sample images I'd find the middle point of the short edges of the bounding box and get two rectangles for the two halves of the big BBox.

I would then compute the sum of the mask pixels in the two separate half-BBoxes, assuming white is 1 and black is 0. Since the white area is bigger on the half of the rectangle where the "front" of the turbine is, pick the direction according to which of the two half-BBoxes has a higher sum

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Nice trick to start with.. However, it depends on how much precision he wants, because the direction of the rectangle depends on the color of the ground and the thresholding (binarization)
Indeed, but given what he presents as example, that' the best I can suggest. His processing is a chain of error-adding operations: segmentation of the turbine, bounding-box estimation and then direction estimation. Of these, the first two operations are more critical than the third, because with a good bounding box the choice of direction boils down to a binary choice

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